The incidence and mortality of cancer have shown a significant increase year by year in China and worldwide [1,2]. At the same time, cancer has become the leading cause of death and a major public health problem in China [3]. Cancer is expected to become the leading cause of death and the most important obstacle to increasing life expectancy in world population in the 21st century, with highly prevalent tumors such as colorectal cancer plays an increasingly important role. In the 2018, the number of new cases of colorectal cancer > 1.8 million and the number of deaths was about 881,000 cases worldwide, among all types of cancers. Colorectal cancer has the 3rd highest incidence (10.2 %) and the 2nd highest mortality (9.2 %) among all types of cancer around the world [4]. It is noteworthy that the incidence of colorectal cancer in developed countries, such as Europe and the United States, has been gradually decreasing, and the incidence and death of colorectal cancer in China have been maintained at a low level for a long time, but in recent years, the incidence has been rapidly increasing and the population is becoming younger.

From the 1970s to the beginning of the 21st century, the standardized incidence of colon cancer increased by 141.38 % and 151.75 % for men and women, respectively, and the standardized incidence of rectal cancer increased by 49.09 % and 27.19 %, respectively, in large cities such as Shanghai. colorectal cancer is prone to distant metastasis, and the liver is the target organ most likely to be involved due to distant metastasis of colorectal cancer. Ultimately 40 to 50 % of colorectal cancer patients die from colorectal cancer liver metastases [5]. Colorectal cancer has seriously affected people's quality of life, life health and increased the burden of family and society [6].

Photodynamic therapy, also known as photochemotherapy, utilizes the special affinity of the photosensitizer hematoporphyrin for tumor tissues, which can preferentially accumulate in tumor tissues after intravenous injection, and then irradiate with certain wavelengths of red light to produce photochemical reactions, thereby achieving the effect of killing tumor cells (including apoptosis, necrosis, autophagy, etc.) [7]. According to the literature [8], photodynamic therapy was first applied to the treatment of clinical tumor patients in 1978, and then has applied in many different areas of oncology [9]. Also in gastroenterology, where it was a few attempts to treat both the premalignant lesion and advanced colorectal cancer [10]. The advantages of photodynamic therapy are that it is a localized, mild and relatively safe treatment modality, in the meantime, it has shown a good promise in cancer precision therapy. The use of nano-photosensitizers, the development of compound light sources, and the search for effective ways to alleviate tumor hypoxia have played an important role in enhancing the therapeutic effect of photodynamic therapy [11]. The existing research results also show that photodynamic therapy seems to be safe and feasible treatment option for colorectal cancer [12].

Compared with other treatments, photodynamic therapy has a long treatment period. The complete metabolism of the photosensitizer takes about 30 days, and there are individual differences. In addition, photodynamic therapy for colorectal cancer patients is performed under endoscopy and requires the assistance of intestinal stents for patients with severe obstruction that prevents fiber optics from reaching the tumor lesion site, etc. Providing whole-course care for colorectal cancer patients during the treatment is essential to increase the efficacy of photodynamic therapy, take care of patients' psychological health, and reduce the incidence of adverse reactions.